dichroic glass having flecks come off in firing

[mbmccann]

I have been firing dichro for several years both capped with clear and uncapped. This week I fired a gold marbles patterned dichro uncapped and some of the gold came off. The flecks got on other pieces nearby. Then I tried the same glass with clear over it and you can kind of see the flecks under the clear. OF course this did stop it from contaminating other jewelry close to it.
Does anyone know about this? Is there a temperature thing that would cure it? I fire to 1450 for my full fuse.

[seachange]

Hi,

I have had exact same thing happening with rainbow two. Long time ago, found out from this board that it is sometimes prone to do this.

Occasionally some of the Profusion patterns silver on black "spit" bits of silver, enough to be annoying. I tend to use a rectangular piece of kilnshelf on its side, as a wall separating these pieces from others in the same firing, to try and avoid ruining the rest.

Lately had a 1/4 disk of stripes, green/magenta blue doing the same. I had to use it uncapped for my work, it was impossible. As you have noticed, even under a clear cap the dichroic looks flecky, instead of being smooth and even. The dichroic is just waste.

Contacted CBS, posted samples of the fired and unfired pieces, they replaced it.

Their response is very good, but certainly does not cover the time wasted in cutting, washing the glass, grinding corners and/or edges, assembling, firing, plus cost of the other accompanying glass (base and or cap), all this work only to find out that the dichroic is faulty. And in my case have to add cost from Australia to freight the faulty pieces, then pay again (had already when I bought the original faulty glass) for freight for the replacement piece.

I haven't found a way to see this prior to firing, except to fire a small sample from each piece. Personally I am not doing this, because it is a lot of extra work, and, in same cases, wasteful as well.

I would recommend contacting CBS. They need to know when their manufacturing is faulty, so that hopefully they'll do something about it.

Sorry I can't offer a solution, only sympathize and tell you you are not the only one this has happened to...hope the cutting and assembly of your pieces was not too complex.

Editing, forgot to add there is no cure.

Best regards, seachange.

[Lynn Perry]

Unfortunately, this is nothing new either. Here is a photo I sent CBS seven years ago when the coating totally shredded (the piece of glass in the middle). The other two pieces were in the same firing with no problems. CBS replaced the full sheet which is pretty much the least they can do other than doing nothing. It is especially irritating now when I pay a premium for ProFusion patterns, who use CBS pretty much exclusively, and the coating popcorns.

Still miss Savoy. Not much variety in colors but never a problem with the coating either capped or uncapped plus the patterns were a bargain compared to ProFusion or Duncan.

[Nancy H]

You may be interested in watching this video http://www.youtube.com/watch?v=NvQUpDon_po
I just stumbled across it this morning myself. Apparently Dichro wants to separate from the glass between 900-1200°F. According to the video, a fast firing temp. between this temp. is needed.
The video suggests this firing schedule for SMALL jewelry pieces.

1500°F/Hour or AFAP to 1425°F 90 COE glass or 1400°F 96 COE glass
Hold for 5-10 min.
NO BUBBLE SOAK
Video doesn't mention annealing.

I haven't tried this myself. Just thought it may pertain to what you are talking about.

[mbmccann]

Thank you so much. I do not hold at 1100 like I do for larger work, but I don't go up that fast. I shall try it next week, before I contact my supplier or CBS.

[Barry Kaiser]

The people at Profusion are quite knowledgable about dichroic glass. In this case however, I think their suggestion is overly cautious. We bubble squeeze dichroic (up) all the time with no ill effects. On very very rare occasion we have had the flecking problem.
If you could not bubble squeeze, you might as well not use it.
Barry

[Lynn Perry]

If you are planning to leave the dichroic uncapped and only firing hot enough for bending, you are toast if you have a coating that peels or even just popcorns (gets a sandy feel). Generally the mixture coatings used for Boxes, Circles, Corkscrew are fine uncapped but fade when capped. Sure do wish CBS would put some of this information on their website rather than letting the customers learn for themselves as well as being the quality control for the coatings that are not properly attached to the substrate. It would be interesting to know how CBS verifies the quality of the coating on each sheet. I have never seen a full or a quarter sheet with a missing corner removed for quality verificiation. Since each sheet is manufactured individually, I don't know how CBS could do random sampling.

[Tom Fuhrman]

I would suggest that some of you visit one or more of the factories that produce this stuff and see what some of the variables are that are very difficult to control. controling the temps of the individual sheet of glass is difficult and many times there are multiple sheets done in one chamber and getting even heating is just like you experience in your kilns.
when patterns are made it is with "masks" and these can effect the heat retention and dispersal of different sheets. Also remember that it is not just one "firing" used to produce these effects, but may require as many as 20. A lot of this could be closer controlled but with greater controls the price increases exponentially and we already complain about the high costs with this material. If you want greater things from the materials, I suggest you try and make dichroics yourself and you'll have a much greater appreciation what it takes to make this material.
If it was a big highly profitable market you woud see more of the scientific and commercial dichroic coaters entering it for art glass.
IMHO; we're fortunate to have a few that have really gone "the extra mile" to make as much as they do for the art glass world.

[mbmccann]

I can appreciate that it is hard to make. However, when I spend $90 for my quarter sheet I need to be able to use it to make attractive jewelry.
I was too busy with a show these last 2 weekends to use the new firing schedule, but I hope it solves the problem. I'll keep you posted.
Thanks for everyone who commented.

[Lynn Perry]

Hi, Tom. I can appreciate the process is difficult, but that seems to me to be all the more reason to document and publish expected results to try to prevent customer dissatisfaction. It is also a good reason to test your product more extensively before you ask your customer to do this for you.

I am glad to have CBS, and I do think they make a beautiful product. Perhaps they need to spend some more time on process control and improvement even if it is at the expense of product output. I really do not appreciate spending my time preparing and firing my work only to have the coating fail or give undesirable results. The offer of replacement glass is the equivalent of the old Kodak guarantee of film to replace the film that failed during your daughter's wedding..... not too much value and not something I would even want to use again.

PS: If CBS needs someone to test their different coatings, I would be happy to do that for them if they send me a quarter sheet of each which need tested. That might actually be less expensive than replacing glass.

[Tom Fuhrman]

If you have a lab that can actually offer a service that is well calibrated and and can hold standards consistent, they may be willing to work with you. There are so many uses and so many different applications for using their materials that I'm certain they can't start to begin to test all the different outcomes. This is why a lot of the other coaters have not pursued serving a larger market.
Can you control your temps to absolute temperatures and have your equipment calibrated to somewhere near ASTM standards? would it be worth it to pay twice to three times as much for the product if you were absolutely certain it would never flake? Some of the stuff they are producing at the best is going to give "spotty" results in many uses.
The answer is that if you try a small bit and it doesn't work for your application use some one else's or use something different. Unless they have control of the entire process, i.e. manufacturing of the glass itself and what may happen at every step aong the way, it makes it difficult to keep tight controls. They spend their time trying to produce new items that will allow artists to venture in new directions and excite them. When they only had a few products it was much simpler to control it all and test it more completely. CBS is just a small family owned manufacturer that offers a service to the artist community
The production of all the different colors and textures of glass and making them compatible is another thing that is a lot more difficult than we give the manufacturers credit for. These companies are no where even a fraction the size of Kodak and they had their problems as you noted.
Enjoy the availability of these products now for I predict that in 15-20 years they will have disappeared as the owners of these small companies are the force and knowhow behind them. Once they are gone, things will change. These people are real artists to be able to produce what they do.

[Lynn Perry]

Hi, Tom. Those are all good points. I think the issue that makes it so important to have a quality dichroic coating is that Profusion and Duncan are etching those coatings and adding another significant price increase. The expectations that those products will perform reliably is even higher and the financial loss when they do not perform is nearly doubled.

I have been moving away from the dichroic glass supply for several years. While I have been able to work around most of the performance problems, the cost of the dichroic glass, especially the patterned glass, has continued to increase while the customer perceived value of the final product has declined. I have not made a full dichroic pendant in three years, and I did not offer any this year to the galleries who represent me. That particular segment of the market has become a commodity and is being driven to the lowest cost, because my customers see all of the pendants as being equal.